Early-onset Bipolar Disorder is Bipolar Disorder that appears in children. It has only been recently that it has been acknowledged that the disorder appears in patients younger than mid- to late-adolescence.

For many years, it was assumed that children could not suffer the mood swings that are characteristic of Bipolar Disorder; however, now researchers have discovered that Bipolar Disorder not only does, in fact, happen as early as the age of toddler, but that it happens much more prevalently that had been thought, and it has been named Early-Onset Bipolar Disorder.

Many parents have reported that their children seemed different from birth, or that they noticed that something was wrong in their children as early as eighteen months. They have said that their babies were often extremely difficult to settle, rarely slept, and experienced separation anxiety.

Children later diagnosed as Early-Onset Bipolar Disorder were reported to have been, when they were younger, hyperactive, inattentive, fidgety, easily frustrated and prone to terrible temper tantrums, especially when the parent used the word 'No.' They have gone into explosions of temper, even rages, and these have gone on for prolonged periods of time; they became quite aggressive and sometimes even violent.

Children with Early-Onset Bipolar Disorder are difficult to diagnose. Many parents are told that the diagnosis cannot even be made until their child is older—at least upper adolescence. This is because the Diagnostic and Statistical Manual of Psychiatry (DSM-IV) uses the same criteria to diagnose Bipolar Disorder in children as it does to diagnose adults. In addition, the manic phase of Bipolar Disorder mimics Attention Deficit Hyperactivity Disorder (ADHD), and the child is sometimes misdiagnosed as having ADHD instead of Bipolar Disorder.

Behaviors reported by parents in children diagnosed with Early-Onset Bipolar Disorder may include: extreme sadness, change in appetite, lack of interest in play, rapidly changing moods, explosive anger and rages, separation anxiety, hyperactivity, agitation, distractibility, sleep problems, bed wetting, night terrors, poor judgment, impulsivity, racing thoughts, risky behavior, inappropriate behavior (especially sexual in nature), delusions and hallucinations.